1 / 17

Motivation

A Scalable Design for a High Energy, High Repetition Rate, Diode-Pumped Solid State Laser (DPSSL) Amplifier. Paul Mason, Klaus Ertel, Saumyabrata Banerjee, Jonathan Phillips, Cristina Hernandez-Gomez, John Collier Workshop on Petawatt Lasers at Hard X-Ray Light Sources

juro
Télécharger la présentation

Motivation

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. A Scalable Design for a High Energy, High Repetition Rate, Diode-Pumped Solid State Laser (DPSSL) Amplifier Paul Mason, Klaus Ertel, Saumyabrata Banerjee, Jonathan Phillips, Cristina Hernandez-Gomez, John Collier Workshop on Petawatt Lasers at Hard X-Ray Light Sources 5-9th September 2011, Dresden, Germany paul.mason@stfc.ac.uk STFC Rutherford Appleton Laboratory, Centre for Advanced Laser Technology and Applications R1 2.62 Central Laser Facility, OX11 0QX, UK +44 (0)1235 778301

  2. Motivation • Next generation of high-energy PW-class lasers • Multi-J to kJ pulse energy • Multi-Hz repetition rate • Multi-% wall-plug efficiency • Exploitation • Ultra-intense light-matter interactions • Particle acceleration • Inertial confinement fusion • High-energy DPSSL amplifiers needed • Pumping fs-OPCPA or Ti:S amplifiers • Drive laser for ICF • Pump technology for HELMHOLTZ-BEAMLINE BeamlineFacility • HELMHOLTZ- BEAMLINE

  3. Amplifier Design Considerations • Requirements • Pulses from 10’s J to 1 kJ, 1 to 10 Hz, few ns duration, efficiency 1 to 10% • Gain Medium • Ceramic Yb:YAG down-selected as medium of choice • Amplifier Geometry

  4. STFC Amplifier Concept ~175K • Diode-pumped multi-slab amplifier • Ceramic Yb:YAG gain medium • Co-sintered absorber cladding for ASE suppression • Distributed face-cooling by stream of cold He gas • Heat flow along beam direction • Low overall aspect ratio & high surface area • Operation at cryogenic temperatures • Higher o-o efficiency – reduction of re-absorption • Increased gain cross-section • Better thermo-optical & thermo-mechanical properties • Graded doping profile • Equalised heat load in each slab • Reduces overall thickness (up to factor of ~2)

  5. Modelling Cr4+:YAG 50% pump region • Laser physics • Assumptions • Target output fluence 5 J/cm² • Pump 940 nm, laser 1030 nm • Efficiency & gain • Optimum doping x length product for maximum storage ~ 50% • Optimum aspect ratio to minimise risk of ASE (g0D < 3) of ~1.5 • Extraction • Extraction efficiency ~ 50% • Thermal & fluid mechanics • Temperature distribution • Stress analysis • Optimised He flow conditions 3.8 Yb:YAG

  6. Scalable Design

  7. DiPOLE Prototype Amplifier • Design sized for ~ 10 J @ 10 Hz • Aims • Validate & calibrate numerical models • Quantify ASE losses • Test cryogenic gas-cooling technology • Test (other) ceramic gain media • Demonstrate viability of concept • Progress to date • Cryogenic gas-cooling system commissioned • Amplifier head, diode pump lasers & front-end installed • Full multi-pass relay-imaging extraction architecture under construction • Initial pulse amplification tests underway Ceramic YAG disk with absorber cladding Yb3+ Cr4+ Diode pump laser

  8. Optical Gain Material Cr4+ Pump2 x 2 cm² • 4 x co-sintered ceramic Yb:YAG disks • Circular 55 mm diameter x 5 mm thick • Cr4+ absorbing cladding • Two doping concentrations (1.1 & 2.0 at.%) 55 mm 35 mm Yb3+ Fresnel limit ~84% PV 0.123 wave 1030 nm 940 nm

  9. Amplifier Head Design • Schematic • CFD modelling Disks Uniform T across pumped region ~ 3K Pump Pump He flow pressure windows Vacuum vacuum windows He flow 40 m3/hr ~ 25 m/s @ 10 bar, 175 K

  10. Diode Pump Laser • Built by Consortium • Ingeneric, Amtron & Jenoptic • Two systems supplied • 0 = 939 nm, FWHM < 6 nm • Peak power 20 kW, 0.1 to 10 Hz • Pulse duration 0.2 to 1.2 ms • Uniform square intensity profile • Steep well defined edges • ~ 80 % spectral power within  3 nm • Good match to Yb:YAG absorptionspectrum @ 175K Measured 20 mm 20 mm

  11. DiPOLE Laboratory Cryo-cooling system Amplifier head 2 x 20 kW diode pump lasers

  12. Front-end Injection Seed Amplifier crystal nsecoscillator • Free-space diode-pumped MOPA design • Built by Mathias Siebold’s team @ HZDR Germany • Cavity-dumped Yb:glass oscillator • Tuneable 1020 to 1040 nm •  ~ 0.2 nm • Fixed temporal profile • Duration 5 to 10 ns • PRF up to 10 Hz • Output energy up to 300 µJ • Multi-pass Yb:YAG boosteramplifier • 6 or 8 pass configuration • Output energy ~ 100 mJ Booster pump diode x3 or x4 Polarisation switching waveplate 100 mJ output

  13. Initial Pulse Amplification Results • Simple bow tie extraction architecture • 1, 2 or 3 passes • Limited by diffraction effects • Injection seed • Gaussian beam expanded to overfill pump region • Energy ~ 60 mJ Seed Amplified beam Pump Pump

  14. Spatial Beam Profiles @ 100K, 1 Hz Gain  8 Gain  6 E = 2.6 J @ 10 Hz

  15. Pulse Energy v. Pump Pulse Duration Onset of ASE loss • 3 passes @ 1 Hz • Relay-imaging multi (6 to 8) pass extraction architecture is required to allow >10 J energy extraction at 175K 5.9 J

  16. Conclusions • Cryogenic gas cooled Yb:YAG amplifier offers potential for efficient, high energy, high repetition rate operation • At least 25% optical-to-optical efficiency predicted • Proposed multi-slab architecture should be scalable toat least 1 kJ generating ns pulses at up to 10 Hz • Limit to scaling is acceptable B-integral • DiPOLE prototype amplifier shows very promising results • Installation of relay-imaging multi-pass should deliver 10 J @ 10 Hz • Strong candidate pump technology for generating high energy, ns pulses at ~ 1 Hz for HELMHOLTZ-BEAMLINE

  17. Thank you for your attention! Any Questions?

More Related